v01d commented on a change in pull request #1705: URL: https://github.com/apache/incubator-nuttx/pull/1705#discussion_r483773149
########## File path: arch/arm/src/nrf52/nrf52_rtc_lowerhalf.h ########## @@ -0,0 +1,58 @@ +/**************************************************************************** + * arch/arm/src/nrf52/nrf52_rtc_lowerhalf.h + * + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. The + * ASF licenses this file to you under the Apache License, Version 2.0 (the + * "License"); you may not use this file except in compliance with the + * License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT + * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the + * License for the specific language governing permissions and limitations + * under the License. + * + ****************************************************************************/ + +#ifndef __ARCH_ARM_SRC_NRF52_NRF52_RTC_LOWERHALF_H +#define __ARCH_ARM_SRC_NRF52_NRF52_RTC_LOWERHALF_H + +/**************************************************************************** + * Included Files + ****************************************************************************/ + +#include <nuttx/config.h> + +#include <nrf52_rtc.h> + +/**************************************************************************** + * Public Function Prototypes + ****************************************************************************/ + +/**************************************************************************** + * Name: nrf52_rtc_initialize + * + * Description: + * Bind the configuration timer to a timer lower half instance and + * register the timer drivers at 'devpath' + * + * Input Parameters: + * devpath - The full path to the timer device. This should be of the + * form /dev/timer0 + * timer - the timer's number. + * timer_drvr - Pointer where to store resulting timer_lowerhalf_s* + * + * Returned Value: + * Zero (OK) is returned on success; A negated errno value is returned + * to indicate the nature of any failure. + * + ****************************************************************************/ + +int nrf52_rtc_initialize(FAR const char *devpath, uint8_t timer, + FAR struct timer_lowerhalf_s **timer_drvr); Review comment: No, RTC does not support auto-clearing. I'm doing this by manually clearing it on interrupt (see `nrf52_rtc_handler`). nRF52 has a peripheral which allows you to tie events to tasks, so you could connect the COMPARE event to the CLEAR task and then it will be taken care of by hardware. However, this uses up one PPI channel which may not be desireable. This is stated in the comment here (expand the _lowerhalf file diff): https://github.com/apache/incubator-nuttx/pull/1705/files#diff-57c967820db5f66391fba3ad66318487R156 Anyway, I also wondered what was the proper way to expose the RTC (via timer or arch_alarm + oneshot). The point is that oneshot interface is designed to work with absolute times, presumably with a real RTC (which does not wrap around in a long time). On up_timer_gettime from arch_alarm.c, the counter is obtained as an absolute value. Since nRF52 RTC is simply a low power timer (with a period of 512 seconds) it would be a lot more complex to offer that interface. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org
